Hmmm… just to give a fuller picture:
It is possible you’ll find someone who’ll run just the bits you need and you could do it in a shorter time, but it’s not that much less time. The likes of Dave does that, but he is freelance, most ADR courses will be run by standard training providers who tend to cater to as broad a selection of candidates as possible - hence the five-day standard course. It’s a question of simple economics.
However, I suspect you won’t easily find a customised setup, and probably if you do find it’s not likely to be reasonably local, if being local is an issue. If you could find the customisation you need, and were only doing Core, Class 3 and Tanks, it could be done in three full days.
On the other hand you could cherry-pick the bits you do need from someone’s standard five day course containing part you don’t need - no training provider will object to catering to that. A typical plan of instruction (there’s a few different variants) would look something like this
Core is day 1 and half of day 2
Packages (should you wish to include that) will be the afternoon of day 2, if not you’ve got the afternoon free
Class 3 will be the first part of Day 3, then you’re free for the rest of that day, until…
Tanks which begins late afternoon of Day 3 and continues through all of Day 4
Day 5 morning will be your exams.
An alternative plan is where exams are done in the early part of day 4 and the tanks module plus the tanks exam take up the afternoon of Day 4 and part of Day 5
So… you’d still need to be available for the full five days in either of those non-custom scenarios
HTH